Add bd cleanup command for bulk deletion of closed issues

Implements bd-jx90: simple cleanup command without API key requirement.

Features:
- Delete all closed issues with --force
- Filter by age with --older-than N (days)
- Preview with --dry-run
- Cascade deletion with --cascade
- JSON output support

Usage:
  bd cleanup --force                    # Delete all closed
  bd cleanup --older-than 30 --force    # Delete >30 days old
  bd cleanup --dry-run                  # Preview

Closes bd-jx90

Amp-Thread-ID: https://ampcode.com/threads/T-8d905db0-4ec7-411e-95de-1f044219dc9c
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/cleanup.go

@@ -0,0 +1,135 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/fatih/color"
+	"github.com/spf13/cobra"
+	"github.com/steveyegge/beads/internal/types"
+)
+
+var cleanupCmd = &cobra.Command{
+	Use:   "cleanup",
+	Short: "Delete all closed issues (optionally filtered by age)",
+	Long: `Delete all closed issues to clean up the database.
+
+By default, deletes ALL closed issues. Use --older-than to only delete
+issues closed before a certain date.
+
+EXAMPLES:
+Delete all closed issues:
+  bd cleanup --force
+
+Delete issues closed more than 30 days ago:
+  bd cleanup --older-than 30 --force
+
+Preview what would be deleted:
+  bd cleanup --dry-run
+  bd cleanup --older-than 90 --dry-run
+
+SAFETY:
+- Requires --force flag to actually delete (unless --dry-run)
+- Supports --cascade to delete dependents
+- Shows preview of what will be deleted
+- Use --json for programmatic output`,
+	Run: func(cmd *cobra.Command, args []string) {
+		force, _ := cmd.Flags().GetBool("force")
+		dryRun, _ := cmd.Flags().GetBool("dry-run")
+		cascade, _ := cmd.Flags().GetBool("cascade")
+		olderThanDays, _ := cmd.Flags().GetInt("older-than")
+
+		// Ensure we have storage
+		if daemonClient != nil {
+			if err := ensureDirectMode("daemon does not support delete command"); err != nil {
+				fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+				os.Exit(1)
+			}
+		} else if store == nil {
+			if err := ensureStoreActive(); err != nil {
+				fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+				os.Exit(1)
+			}
+		}
+
+		ctx := context.Background()
+
+		// Build filter for closed issues
+		statusClosed := types.StatusClosed
+		filter := types.IssueFilter{
+			Status: &statusClosed,
+		}
+
+		// Add age filter if specified
+		if olderThanDays > 0 {
+			cutoffTime := time.Now().AddDate(0, 0, -olderThanDays)
+			filter.ClosedBefore = &cutoffTime
+		}
+
+		// Get all closed issues matching filter
+		closedIssues, err := store.SearchIssues(ctx, "", filter)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Error listing issues: %v\n", err)
+			os.Exit(1)
+		}
+
+		if len(closedIssues) == 0 {
+			if jsonOutput {
+				result := map[string]interface{}{
+					"deleted_count": 0,
+					"message":       "No closed issues to delete",
+				}
+				if olderThanDays > 0 {
+					result["filter"] = fmt.Sprintf("older than %d days", olderThanDays)
+				}
+				output, _ := json.MarshalIndent(result, "", "  ")
+				fmt.Println(string(output))
+			} else {
+				msg := "No closed issues to delete"
+				if olderThanDays > 0 {
+					msg = fmt.Sprintf("No closed issues older than %d days to delete", olderThanDays)
+				}
+				fmt.Println(msg)
+			}
+			return
+		}
+
+		// Extract IDs
+		issueIDs := make([]string, len(closedIssues))
+		for i, issue := range closedIssues {
+			issueIDs[i] = issue.ID
+		}
+
+		// Show preview
+		if !force && !dryRun {
+			fmt.Fprintf(os.Stderr, "Would delete %d closed issue(s). Use --force to confirm or --dry-run to preview.\n", len(issueIDs))
+			os.Exit(1)
+		}
+
+		if !jsonOutput {
+			if olderThanDays > 0 {
+				fmt.Printf("Found %d closed issue(s) older than %d days\n", len(closedIssues), olderThanDays)
+			} else {
+				fmt.Printf("Found %d closed issue(s)\n", len(closedIssues))
+			}
+			if dryRun {
+				fmt.Println(color.YellowString("DRY RUN - no changes will be made"))
+			}
+			fmt.Println()
+		}
+
+		// Use the existing batch deletion logic
+		deleteBatch(cmd, issueIDs, force, dryRun, cascade, jsonOutput)
+	},
+}
+
+func init() {
+	cleanupCmd.Flags().BoolP("force", "f", false, "Actually delete (without this flag, shows error)")
+	cleanupCmd.Flags().Bool("dry-run", false, "Preview what would be deleted without making changes")
+	cleanupCmd.Flags().Bool("cascade", false, "Recursively delete all dependent issues")
+	cleanupCmd.Flags().Int("older-than", 0, "Only delete issues closed more than N days ago (0 = all closed issues)")
+	rootCmd.AddCommand(cleanupCmd)
+}